The invention relates to an x-ray diagnostic generator comprising a high voltage transformer, a high voltage rectifier and an x-ray tube connected thereto, in which a switch and control tube lies in the x-ray tube circuit and is connected to a control arrangement which supplies a control voltage to the grid of the switch and control tube for determining the x-ray tube voltage.
An x-ray diagnostic generator of this type is described in the German Pat. No. 1,005,204. In this x-ray diagnostic generator, the switch and control tube is developed as a triode and lies, with its cathode-anode segment, in the connection between two sections of the high voltage rectifier. In order to switch off the x-ray tube, a negative potential is applied to the control grid of the switch and control tube, so that this blocks. Thereby, the full open circuit voltage lies across the cathode-anode segment, so that the switch and control tube must be dimensioned accordingly.
To effect a reduction of the voltage load across the switch and control tube, it is known through the German Offenlegungsschrift No. 2,037,767 to provide a grid-controlled x-ray tube and to switch the x-ray tube on and off via the control grid. It is also already known (British Specification No. 1,077,742) to interpose two switch and control tubes in series with the x-ray tube. In this case, only half of the open-circuit voltage lies across one switch and control tube in the moment of switching off. A switch and control tube is a relatively expensive component part, so that the utilization of two such component parts greatly increases the cost of the x-ray diagnostic apparatus.